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Financial instruments - Additional Information (Details) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jul. 01, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jul. 01, 2018 USD ($)	Mar. 04, 2019 USD ($) Financial_Institution_Counterparty	Mar. 04, 2019 EUR (€) Financial_Institution_Counterparty	Dec. 31, 2018 USD ($)	Oct. 04, 2018 USD ($) Financial_Institution_Counterparty	Oct. 04, 2018 EUR (€) Financial_Institution_Counterparty
Derivatives Fair Value [Line Items]
Foreign currency translation, continuing operations, adjustments, net of tax	$ 12,568,000	$ (125,705,000)	$ 12,332,000	$ (44,517,000)
Net revenues	652,507,000	609,866,000	1,266,091,000	1,197,096,000
Allowance for doubtful accounts receivable	9,900,000		9,900,000				$ 9,300,000
Allowance for doubtful accounts receivable, current	5,200,000		5,200,000				4,400,000
Cash flow hedging
Derivatives Fair Value [Line Items]
Ineffectiveness related to derivatives	0	0	0	$ 0
Foreign exchange contract \| Designated as Hedging Instrument \| Cash flow hedging
Derivatives Fair Value [Line Items]
Total notional amount for all open foreign currency forward contracts	118,100,000		118,100,000				115,300,000
Foreign exchange contract \| Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Gain related to currency forward contracts	1,500,000	$ 1,400,000	700,000
Loss related to currency forward contracts			1,600,000
Total notional amount for all open foreign currency forward contracts	147,500,000		147,500,000				$ 125,900,000
Cross-currency interest rate swap \| Cash flow hedging
Derivatives Fair Value [Line Items]
Foreign currency translation, continuing operations, adjustments, net of tax	$ 700,000		$ 9,800,000
Cross-currency interest rate swap \| Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Total notional amount for all open foreign currency forward contracts					$ 250,000,000	€ 219.2		$ 500,000,000	€ 433.9
Derivative, number of instruments held \| Financial_Institution_Counterparty					5	5		6	6
Derivative, fixed interest rate					4.875%	4.875%		4.625%	4.625%
Derivative, annual interest rate					2.4595%	2.4595%		1.942%	1.942%